I have a 2010 mini cooper base 1.6 that misfires when warm and runs perfect when cold. I have misfire codes and oxygen sensor code. The cylinder that has a noticeable misfire is cyl 3. I have tried moving coil, injector, and spark plug to a different cylinder and misfire stays in cyl 3. I have checked compression and all cylinders are good. I have also checked fuel pressure and it is good and stable when cold and warm. I have seafoamed and issue remains the same. I have noticed that when misfire begins when warm if I disconnect either cam sensor or either vanos solenoid the misfire stops and idles smooth again. Any one have any ideas on what it can be?

 

I'd be curious if your VANOS may be clogged. I'd maybe pull the VANOS and cam sensor and clean them. Below, the red arrow shows a partially restricted solenoid and the green arrow shows a fully restricted solenoid. Your issue sounds similar to this one HERE. He ended up cleaning the cam sensor and his issue was resolved. Post #45 is the resolution. May not hurt to test it out and see if it makes a difference and then go from there.

 

I have taken the sensors off and solenoids as well and at first has some build up on them but I cleaned and reinstalled and same issue. It does seem like this car didn't have the oil changed often. Wonder if passages as blocked

 

You may have to replace the VANOS. I have seen more than a few instances of cleaning a VANOS not resolving the issue, but replacing it did. You can test the unit to be sure. If you find it to be the issue we have them here: http://www.pelicanparts.com/cgi-bin/...-8-610-388-M26. This is the newest revision VANOS unit.

 

How can I test the solenoid?

 

ANYONE?? I have the exact same problem, I've even swapped one known good VANOS solenoid into the car
and 2 known good camshaft position sensors, but have a continuous misfire on cylinder 1, replaced all spark plugs and coils- oem mini..compression test results good.... can anyone help? Thanks

 

What were the compression test numbers? Did you swap injectors? What is your MINI info (year, model) and what P code are you getting, just P0301? How do you know the VANOS solenoid or camshaft sensors were good? Were they new? Have you done a leak down test?

https://www.obd-codes.com/p0301

 

2010 mini clubman non-s (N12 engine) compression test numbers were around 165psi for cylinder #1 and the others were within 10psi of each other... injectors were swapped and misfire did not follow. The VANOS installed in the vehicle are the new design and not clogged, I recently acquired the vehicle with this problem so I don't know it's past. The parts I replaced are ignition coils, spark plugs all mini original dealer parts. I swapped both cam sensors and only one VANOS solonoid with ones from a 2011 mini cooper that runs and drives without faults. I'm only getting P0301 with a generic scanner but with ISTA/D I'm getting cylinder 1 misfire and random cylinder misfire. I've tested VANOS and everything reaches its set points and passes test plans.... no leak down test performed..... if I disconnect any cam sensor or VANOS electrical connector the car hiccups and then runs normal, the engine no longer misfires as viewed from misfire status..... any ideas?

 

Buller?.... anyone? Seems to me someone's had to have encountered this problem before?

 

What I suggest you do is copy and paste this into the comments & suggestions section at the bottom of this tech article here: http://www.pelicanparts.com/techarti...or_Testing.htm. Our MINI guru Nick might have some additional input for you.

 

Still no reply...... I posted on that forum and the "guru" Nick replied and said bad exhaust valve because of compression readings... I replied back with the actual numbers... he didn't respond back.... if it is mechanical... an exhaust valve... why when I disconnect any valve timing sensor electrical signal the car hiccups and then drives and idles without misfire??? Someone with some advice?

 

Has anyone fixed this problem yet as I haven't?

 

No one has ever solved this mystery?? Strange that the forum has no solution when it seems it's not just one person, and I noticed we all have 2010 Base Coopers with N12 Engines. I'd really like to solve this and get this car back to normal.

 

If it misfires on tick over when hot your problem is the cylinder head.
When engine is warming up it uses airflow butterfly to accelerate but when it gets to running temperature the butterfly is fully open and the second inlet camshaft takes over.
The valves open further as you accelerate. At tick over the inlet valves only opens 1/3 of a mm.
What happens engine gets hot and the hardens valve seats drop slightly stopping valve from opening properly.
My Mini Cooper would run OK when cold but when hot on tick over number 1 cylinder would misfire.
Disconnecting valve timing sensor makes the engine go into default back to using the butterfly .
I changed all the usual parts but number i cylinder still mis fired.
I bought a second hand cylinder head which I knew was good and fitted it to my engine.
Went for test run engine warmed up and tick over on all cylinders working as it should.

 

Thank you for replying. To be sure I understand correctly, what exactly is the butterfly you're referring to? The throttle plate? Or is it the somewhat odd shaped lobe on the second Cam Shaft. I'm assuming Tick over time is when the time when the second Cam shaft activates or deactivates? My car did this for about a month a year ago (2010 R57 Non-S N12 Engine) and somehow this problem went away on its own, the only thing I had changed was a fuel filter I had scheduled. While pondering on what was going on, the problem simply vanished for a whole year. Fast forward Oct 2020 and I had a bad head gasket. Took head off, sent to machine shop, got a valve job done, no warp on head or anything. Got the head back, reassembled and everything ran fine for a few weeks and now the problem has returned.

Is this something visible to the naked eye using a boroscope in the cylinder when vehicle is at operating temperature? Also, sometimes it will run fine even when hot, and if I turn it off and back on it starts the misfire. Not sure the valve seat would suddenly drop because I turned the car off then on?

 

Butterfly is in air intake that opens to let air in to inlet manifold.
When engine is hot the second cam activates and butterfly is fully open.
From this point to make the engine rev the second cam has a motor which alters cam so valves open wider letting in more air in.
This problem usually happens when the engine has been over heated which loosens the valve seats.
I tried changing every part which did not fix problem so I phoned a MINI specialists in Mini problems in Manchester.
I was directed to a cylinder head specialists who told me the problem.
I bought a second hand head and fitted it problem solved

 

This all makes sense because I remember having a bad thermostat (this car is primarily driven by my wife) and I’m not sure how long the TStat was bad and if vehicle had overheated but eventually it did show Head gasket symptoms which I resolved last month.

I wasn’t entirely sure how and when the second cam works. I appreciate your replies. Is there no way to repair this in a machine shop? Not sure but If I remember correctly, but I think my machine shop did not touch the seats, I think they only changed the guides.

 

I only fitted a second hand cylinder head as they are cheep paid £60 ($78) for it.
Over here there is a lot being broken so spares are cheep.
Machine shop needs to pull old harden seats out then replace them sealing them in place.
Did you use new head and vanos bolts as they are stretch bolts (use only once).